271 NATIONAL INSTITUTE FOR CLINICAL EXCELLENCE INTERVENTIONAL PROCEDURES PROGRAMME Interventional procedures overview of cryoablation for atrial fibrillation as an associated procedure with other cardiac surgery Introduction This overview has been prepared to assist members of the Interventional Procedures Advisory Committee (IPAC) in making recommendations about the safety and efficacy of an interventional procedure. It is based on a rapid review of the medical literature and specialist opinion. It should not be regarded as a definitive assessment of the procedure. Date prepared This overview was prepared in July 2004. Procedure name • Cryoablation for atrial fibrillation as an associated procedure with other cardiac surgery. Specialty society • Society of Cardiothoracic Surgeons in Great Britain and Ireland. • British Pacing and Electrophysiology Group. Description Indications Atrial fibrillation. Atrial fibrillation is the irregular and rapid beating of the upper two chambers of the heart (the atria). It may be classified as paroxysmal, persistent or permanent. It is the most common type of arrhythmia, affecting approximately 0.5% of the adult population1. The incidence increases markedly with age. Patients with atrial fibrillation may be asymptomatic or they may have symptoms including palpitations, dizziness and breathlessness. They also have an increased risk of stroke, as a result of blood clots forming in the left atrium and then embolising to the brain. Although atrial fibrillation may occur in the absence of other heart disease, it is particularly common in patients with mitral valve disease. Patients with a history of atrial fibrillation for longer than a year are less likely to be restored to normal sinus rhythm after mitral valve surgery alone than patients with intermittent atrial fibrillation or those who have had atrial fibrillation for less than a year. IP overview: cryoablation for atrial fibrillation with other cardiac surgery Page 1 of 13 271 Current treatment and alternatives Conservative treatments include medications to control the heart rhythm and rate, electrical cardioversion and anticoagulants to prevent blood clots forming. A surgical approach known as the Cox maze procedure was developed to treat atrial fibrillation. This is usually performed at the same time as open heart surgery for another indication, such as mitral valve disease. Multiple strategically placed incisions are made in both atria to isolate and stop the abnormal electrical impulses. All the incisions are then sutured and a ‘maze’ of scar tissue subsequently forms at the incision sites, which blocks the electrical impulses from travelling through the atrium. A single pathway is left intact for the impulse to travel between the chambers of the heart. What the procedure involves Cryoablation of the atria can be performed via a catheter introduced through a femoral vein but surgical cryoablation for atrial fibrillation is typically carried out in patients undergoing concomitant open-heart surgery, including mitral valve replacement or repair. Cryoablation is sometimes used during the Cox maze surgical procedure to replace some of the incisions but it has been used more recently to recreate the whole standard lesion set of the traditional Cox maze surgery. Ablation may be carried out on both atria or on the left atrium only. Cardiac surgery is usually performed through a median sternotomy. The patient is connected to a cardiopulmonary bypass machine and an incision is made to enter the left atrium. Cryoablation may be performed before or after the concomitant cardiac surgical procedure. A cryoprobe is used to freeze tissue along a pattern of lines in the left atrium. Following freezing, the damaged tissue forms scars that disrupt the transmission of the electrical impulses. The procedure may then be repeated in the right atrium. The ablation can be performed from within or outside the atrium. Cryoablation is faster than the traditional Cox maze procedure. Efficacy One non-randomised trial compared patients treated with mitral valve surgery and cryoablation with patients having mitral valve surgery and the conventional surgical maze procedure. 85% (94/110) of patients treated with cryoablation were in sinus rhythm at discharge, compared with 86% (95/110) of patients treated with the conventional maze surgery (p = 0.84). The survival rate at 3 years was 92% for the cryotherapy group and 98% for the conventional maze group (p = 0.32). Two non- randomised trials compared patients having cryoablation and heart valve surgery with patients having heart valve surgery only. In the cryoablation groups 100% (36/36) and 78% (25/32) of patients were in sinus rhythm immediately after surgery, compared with 33% (5/15) and 22% (4/18) of patients in the control groups. In one of these studies, 90% (26/29) of patients treated with cryoablation were in sinus rhythm at 9 months, compared with 25% (4/16) of patients in the control group (p < 0.0005). In the other study, 78% (28/36) of patients treated with cryoablation and 20% (3/15) of patients in the control group were in sinus rhythm at 6 months (p < 0.05). The Specialist Advisors did not raise any specific concerns regarding the efficacy of the procedure. IP overview: cryoablation for atrial fibrillation with other cardiac surgery Page 2 of 13 271 Safety Because the cryoablation is performed with concomitant cardiac surgery, it is sometimes difficult to differentiate those complications that are specifically related to the cryoablation procedure. Three studies reported the rate of in-hospital mortality, which ranged from 0% (0/28) to 3% (3/95). Four studies reported that between 3% (1/32) and 14% (4/28) of patients required a pacemaker to be implanted. Other complications that were reported less commonly included reoperation, delayed cardiac tamponade, mediastinitis, low cardiac output, intra-aortic balloon pump, dialysis, and transient ischaemic attack. The Specialist Advisors noted that heart block damage to the circumflex coronary artery, intraoperative myocardial infarction, and oesophageal injury were potential adverse effects of the procedure. Literature review Rapid review of literature The medical literature was searched to identify studies and reviews relevant to intraoperative cryoablation for atrial fibrillation as an associated procedure with other cardiac surgery. Searches were conducted via the following databases, covering the period from their commencement to July 2004: MEDLINE, PREMEDLINE, EMBASE, Cochrane Library and Science Citation Index. Trial registries and the Internet were also searched. No language restriction was applied to the searches. The following selection criteria (Table 1) were applied to the abstracts identified by the literature search. Where these criteria could not be determined from the abstracts the full paper was retrieved. Table 1 Inclusion criteria for identification of relevant studies Characteristic Criteria Publication type Clinical studies included. Emphasis was placed on identifying good quality studies. Abstracts were excluded where no clinical outcomes were reported, or where the paper was a review, editorial, laboratory or animal study. Patient Patients with atrial fibrillation and requiring concomitant cardiac surgery. Intervention/test Intraoperative cryoablation of the atria. Outcome Articles were retrieved if the abstract contained information relevant to the safety and/or efficacy. Language Non-English-language articles were excluded unless they were thought to add substantively to the English-language evidence base. List of studies included in the overview This overview is based on three non-randomised controlled trials and three case series studies. One non-randomised controlled trial comparing intraoperative cryoablation with conventional maze surgery was identified.2 Two non-randomised controlled trials comparing patients given heart valve surgery with cryoablation and patients given heart valve surgery only are summarised in Table 2.3,4 Three case series, including a total of 163 patients, are also described.5,6,7 IP overview: cryoablation for atrial fibrillation with other cardiac surgery Page 3 of 13 271 Table 2 Summary of key efficacy and safety findings on intraoperative cryoablation for atrial fibrillation with concomitant cardiac surgery Study Details Key efficacy findings Key safety findings Comments Nakajima H (2002)2 Mean cardiopulmonary bypass time : Complications No randomisation. • cryoablation = 186 minutes Reexploration for bleeding: Non-randomised controlled trial • conventional maze = 214 minutes, p = 0.001 • cryoablation = 2% (2/110) The choice of procedure • conventional maze = 5% (5/110), depended on the period when 1992 – 2001 Sinus rhythm at discharge: p = 0.25 the operation was performed. • cryoablation = 85.4% (94/110) Delayed cardiac tamponade: Japan • conventional maze = 86.4% (95/110), p = 0.84 • cryoablation = 2% (2/110) 110 pairs of patients were • conventional maze = 0% (0/110), matched on age, preoperative 220 patients: Perioperative recurrence of AF: p = 0.15 duration of AF > 10 years, • 50% (110/220) mitral valve • cryoablation = 54% (59/110) High dose of inotropes needed preoperative dimension of left surgery and cryoablation • conventional maze = 60% (66/110), p = 0.34 postoperatively: atrium > 70 mm, history of • 50% (110/220) mitral valve • cryoablation = 0% (0/110) previous cardiac surgery, and surgery and conventional maze Actuarial survival rate at 3 years: • conventional maze = 5% (5/110), concomitant